This invention is related to optical devices for analyzing signal features at multiple optical wavelengths and is particularly adapted to monitoring a plurality of wavelength communication channels in an optical network.
Current optical networks typically use a particular wavelength of light to define a communication channel so that multiple communication channels can be carried on a single optical fiber. DWDM (Dense Wavelength Division Multiplexing) networks are such networks in which an ITU (International Telecommunications Union) standard specifies the particular channel wavelengths and the spacings between these channels. DWDM is based upon WDM (Wavelength Division Multiplexing), an earlier ITU standard in which a smaller number of wavelength channels are carried by an optical fiber with the channels further spaced apart. It should be noted that the term DWDM, as used herein, refers to the more inclusive sense of wavelength definition of communication channels so as to include the ITU WDM and DWDM standards, unless specifically stated otherwise.
To properly administer the increasing load of data, voice and video information signals transported over optical networks, optical channel monitors (OCMs) are used to measure the wavelength, power and signal-to-noise ratio of each communication channel. Many different optical elements have been used in OCMs to decompose optical fiber signals into their wavelength components for monitoring. These elements include wavelength dispersive elements, such as gratings, Fabry-Perot etalons, thin film filters, linear variable filters, and AWGs (Array WaveGuides). Single and arrays of multiple photodetectors are used to detect the dispersed wavelength signals. Nonetheless, despite varied arrangements of such optical elements, OCMs still suffer from numerous infirmities, including poor or slow performance, and high costs of manufacture.
The present invention solves or substantially ameliorates these problems. Furthermore, the present invention is also adaptable to function as an analyzer device for measuring properties of light at multiple optical wavelengths, such as an optical performance monitor, an optical wavelength meter, a DWDM spectrum analyzer, an optical spectrometer, and other instruments which analyze light by its constituent wavelengths.